Energy saving considerations and the use of insulating materials require that vapour is kept under control and its diffusion through the roof is deterred. Perfect indoor humidity control results in improved physiological health.
ROOF VENTILATION (cold roof) If the roof is of ventilated type, there is a need to keep the diffusion of vapour under control, in order to prevent the formation of condensation, which has harmful effects on the insulation. Vapobar has the important function of controlling indoor-outdoor vapour flow, while Diftbar ensures that the roof is breathable. Both Vapobar and Diftbar need to have an SD factor that decreases from the inside towards the outside.
NON-VENTILATED ROOF (warm roof) In a "warm roof" (i.e. non-ventilated roof), the vapour cannot escape from the roof. Alubar keeps vapour from getting into the insulation, where it is liable to result in the rapid deterioration of the entire roofing system. With Alubar, insulation thickness has to be adjusted so that vapour is always cooled to the dew-point above the membrane.
